Method for transmitting data between at least one transmitter and at least one receiver, transmitter, receiver, and transmission system thereof

ABSTRACT

This invention relates to a method for transmitting data between at least one transmitter and at least one receiver, in the form of packets of at least one data item, each of said packets being associated with an identifier of said packet, said receiver periodically sending a feedback message to said transmitter, comprising at least one bitmap block associated with a predetermined number of data packets having consecutive identifiers, so as to selectively inform said transmitter of a state of acknowledgement (acknowledged or unacknowledged) of each of said data packets of said block. 
     According to the invention, this method comprises at least one step of associating at least one timer with at least some of said bitmap blocks.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of data transmission between atransmitter and a receiver. More precisely, the invention relates to allcommunication systems requiring high data transmission quality, and isof special interest for communication systems subject to real timeconstraints.

In particular, but not exclusively, the invention is applied to ARQ(Automatic Repeat Request) type transmission protocols, which implementerror-checking functions within communication systems. Such ARQprotocols define a set of data transmission rules, structured insuccessive frames, as packets.

2. Related Background Art

Many error-checking techniques are generally used in communicationsystems to compensate for loss and/or degradation of data transmittedfrom a source point to a destination point. Conventionally, the errorchecking implements transmission error detection and retransmission oflost or degraded data. According to a known data retransmissiontechnique, the transmitter waits until it has received an explicitdiscard message from the receiver for data lost or degraded duringtransmission, in the form of a feedback message, then retransmits assoon as possible the data unacknowledged by the receiver.

SUMMARY OF THE INVENTION

The invention is applied in particular as part of the ARQ errordetection and retransmission protocol of the HiperLAN/2 (HighPerformance Local Area Network Type 2) standard defined by ETSI(European Telecommunications Standards Institute) in ETSI standard TS101 761-1 V1.1.1 (2000-04) entitled Broadband Radio Access Network(BRAN); HiperLAN Type 2; Data Link Control (DLC Layer) Part 1: BasicData Transport Functions).

The HiperLAN/2 communication standard, also called H/2, defines ahigh-speed low-range radio access system, and is advantageously appliedto wireless local area networks, and wireless access networks. H/2 is acellular system wherein each radio cell is controlled by an accesspoint, called AP, covering a given geographical area, and handling radioresource distribution among the various mobile terminals (called MT) ofthe system. H/2 provides three types of transmission, i.e. uplink,downlink, and direct link transmission.

The HiperLAN/2 ARQ protocol is an ARQ protocol of the “Selective Repeat”type, having several additional mechanisms. The following is adescription of the general principle of this protocol.

An identifier, also called sequence number, is inserted by the ARQtransmitter into each user data packet, also called U-PDU (User ProtocolData Unit), transmitted to the ARQ receiver. This identifier has a10-bit length, and is incremented by 1 modulo 2¹⁰=1024.

Hereafter, the term PDU will designate a U-PDU type user data packet.

The transmitter maintains a list of the sequence numbers it is allowedto transmit, and the receiver maintains a list of the sequence numbersit is prepared to receive. Each of these lists is designed as a PDUwindow. The sequence number activates the receiver to detect a PDU loss,or the reception of a damaged PDU, and to inform the transmitter thereofvia a feedback message. The transmitter then performs a retransmissionof the PDUs incorrectly received by the receiver.

A PDU window is characterized by the variable BoW (Bottom of Window), onthe one hand, and by its size K_(s), on the other hand.

On the transmitter side, BoW is the smallest sequence number associatedwith a PDU that has not yet been positively acknowledged by thereceiver. K_(s) is then the maximum number of PDUs that can be sent andstored in the window waiting for acknowledgement.

On the receiver side, BoW is the smallest sequence number associatedwith a PDU that has not yet been received properly by the receiver.K_(s) is then the maximum number of PDUs that can be accepted and storedin the receive window, before one of these PDUs is transmitted to ahigher layer.

In addition to the sequence number, the ARQ receiver or transmittermaintains an acknowledge state variable for each PDU of the windowindicating whether the PDU has been received properly or not.

In the HiperLAN/2 ARQ protocol, each data packet, or PDU, of a receivewindow is acknowledged selectively within a bitmap block, or by acumulated feedback message if all the PDUs preceding or surrounding thePDU under consideration in the window, including the considered PDUitself, have been received properly.

This bitmap block is associated with a predetermined number of PDUs (8for HiperLAN/2) having consecutive sequence numbers. This association isperformed as follows: the sequence number space, starting at sequencenumber 0, is divided into consecutive sequence number intervals, eachinterval being associated with a given bitmap block. A given marker bitwithin a bitmap block is associated with the sequence number having thesame position within the associated interval of sequence numbers. Thus,a binary value of 1 within a bitmap block indicates that the PDU, thesequence number of which is associated with the bit involved, isacknowledged positively. Conversely, a binary value of 0 within a bitmapblock indicates a negative acknowledgement of the corresponding PDU.

The bitmap block number corresponds to the position occupied by theinterval of sequence numbers with which it is associated, within thesequence number space. A feedback message can transport up to threedistinct bitmap blocks.

The ARQ link established between the transmitter and the receiver ismoreover characterized by the total duration of an operating cycle, alsocalled RTT (Round Trip Time). The RTT duration can be defined as the sumof the time the ARQ transmitter requires for sending a PDU, the time theARQ receiver requires for receiving, processing, and sending a reply tothe transmitter as a (positive or negative) feedback message, and thetime the transmitter requires for analysing this feedback message andreading the receiver's reply therefrom regarding the PDU involved.

As part of HiperLAN/2, the receiver's reply regarding theacknowledgement of a PDU received can be delayed until a certain numberof PDUs have been received, or can be delayed unintentionally by thereceiver if no resource is available for transmitting it. Therefore, theRTT duration varies for a given ARQ link.

This RTT duration moreover depends on the ARQ class of the transmitterand the receiver of the ARQ link involved. It is recalled that the ARQprocessing time of a transmitter is equal to the minimum number offrames passing before the transmitter can transmit PDUs in response toreceiving a feedback message from the receiver. Also, the ARQ processingtime of a receiver is equal to the minimum number of frames passingbefore the receiver can transmit a feedback message in response toreceiving one or more PDUs. The ARQ delay classes defined in HiperLAN/2,having a value of 0, 1, 2, or 3, have a direct impact on the processingtimes of a given ARQ entity (for transmit and receive). Delays have thesame value as the class.

Moreover, each ARQ entity states its ARQ class when transmitting andreceiving during a so-called association period, within the H/2 network.Thus, each ARQ entity, on both sides of a transmission path, candetermine the likely RTT minimum value, as well as the RTT upper limitthat should normally not be reached.

A disadvantage of the known data transmission techniques implementing aretransmission of lost or degraded data upon explicit acknowledgement,is that they offer no adequate solutions in case a feedback message islost or degraded.

Indeed, when a feedback message is lost or degraded, the transmitterdoes not know which PDUs to retransmit. It must therefore wait tocorrectly receive a new feedback message, replacing the lost one,containing all or part of the acknowledge data of the lost message, inorder to implement the mechanism of retransmitting the unacknowledgeddata.

Moreover, if the data exchange protocol does not allow the transmitterto request a specific feedback message or bitmap block, as is the casefor instance in the HiperLAN/2 ARQ protocol, the transmitter is unableto predict the time when it will receive the expected feedback message.

This disadvantage can be a problem when the contents of the feedbackmessage are very important to the transmitter, especially if thefeedback message contains information required by the transmitter formoving the window of PDUs to be transmitted.

For certain applications requiring high-speed data transmission, and inparticular for applications subject to real time constraints, thetransmitter can make the decision, in case of non receipt or latereceipt of a feedback message, not to retransmit the unacknowledgedPDUs. In particular, the object of this discard phenomenon is to preventthe transmitter from retransmitting data that would be useless to thereceiver, because they would be received too late to be taken intoaccount.

Conversely, still e.g. as part of a delay-sensitive radio transmission,a late retransmission of PDUs previously received improperly can alsolead to the implementation of a discard mechanism, this time on behalfof the receiver.

This data loss at the receiver implies a quality degradation of theapplication implemented at the receiving end, in particular when thisapplication is especially sensitive to both data loss and delay.

Another disadvantage of certain prior art techniques, and in particularof the HiperLAN/2 ARQ protocol, is that they offer no solution to copewith possible operating inconsistencies at the receiver. Thus, accordingto the H/2 standard, as the way the receiver transmits feedbackmessages, and the choice of their contents (especially the choice of thebitmap blocks they contain) are not standardized, certain bitmap blockscan be transmitted with a very long delay, and in the worst casescenario, even never be transmitted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of the various steps implemented accordingto the basic inventive mechanism as part of data packet exchangesbetween an ARQ transmitter and receiver;

FIG. 2 shows the PDU exchanges between an ARQ transmitter and receiver,when a timer is associated with each of the bitmap blocks according tothe method of FIG. 1;

FIG. 3 shows a development of the embodiment of FIG. 2, according towhich a time stamp is associated with the unacknowledged PDUs exchangedbetween the ARQ transmitter and receiver;

FIGS. 4 a and 4 b describe PDU exchanges between an ARQ transmitter andan ARQ receiver according to an embodiment similar to that of FIG. 3,with a different RTTmax value corresponding to the maximum duration ofone operating cycle;

FIG. 5 shows a sample PDU transmission between an ARQ class 0transmitter and an ARQ class 1 receiver, according to a similarembodiment as in FIGS. 3 and 4.

DETAILED DESCRIPTION

In particular, the object of the invention is to compensate for thesedisadvantages of prior art.

More precisely, it is an object of the invention to provide a datatransmission technique implementing error detection and retransmissionof lost or damaged data, offering an optimised solution to the problemof a feedback message getting lost or degraded.

It is also an object of the invention to implement a data transmissiontechnique making it possible to compensate for the disadvantages ofprior art techniques according to which, on the one hand, thetransmitter does not have specific means for requesting a specificfeedback message or bitmap block, and, on the other hand, it can beconfronted with possible operating inconsistencies of the receiver.

It is another object of the invention to implement a data transmissiontechnique, especially but not exclusively adequate for the ARQ protocol,in particular for the HiperLAN/2 standard.

Furthermore, it is an object of the invention to provide a datatransmission technique allowing anticipated retransmission ofunacknowledged data packets, in case a feedback message is lost ordegraded.

It is also an object of the invention to implement a technique forcommunicating between a transmitter and a receiver with hightransmission quality.

As part of ARQ-type protocols, it is another object of the invention toavoid untimely implementation of the discard mechanism, in particularenvisaged by the HiperLAN/2 standard.

The above objects as well as others that will be apparent hereafter, areachieved by means of a method for transmitting data between at least onetransmitter and at least one receiver, in the form of packets of atleast one data item, each of said data packets being associated with anidentifier of said packet, said receiver periodically sending to saidtransmitter a feedback message comprising at least one bitmap blockassociated with a predetermined number of data packets havingconsecutive identifiers, so as to selectively indicate to saidtransmitter a state of acknowledgement (acknowledged or unacknowledged)of each of said data packets of said block.

According to the invention, this transmission method comprises at leastone step of associating at least one timer with at least some of saidbitmap blocks, determining a timeout period beyond which a specificoperation is to take place, if no acknowledgement has been received.

Thus, the invention is based on a totally innovative and inventive dataretransmission approach as part of a communication protocol based onerror detection and retransmission of lost or damaged data. Indeed, theprinciple of conventional transmission protocols is based on theimplementation of a data retransmission mechanism in response toreceiving a feedback message indicating that certain PDUs have not beenreceived correctly. According to the invention, the association of atimer with some bitmap blocks makes it possible to implement anticipateddata retransmission, prior to receiving a corresponding feedbackmessage.

It will be noted that a bitmap block is associated with a predeterminednumber of data packets, which can be fixed or variable, but is known tothe transmitter for the whole duration of the communication with thereceiver.

Associating a timer with a bitmap block clearly appears to be a resourceintensive mechanism, but advantageously allows to improve the quality ofservice provided at the receiving end. Therefore, the inventioncontradicts the prejudices of those skilled in the art, who considerthat the quality of service provided is related to maximizing datatransmission throughput, and who consider the resources of acommunication system are therefore to be saved.

Advantageously, for a given bitmap block, this method comprises a firststep of activating said timer, when said transmitter sends to saidreceiver the first of said data packets of consecutive identifiersassociated with said block, so that the timer switches to said activatedstate.

Triggering the timer associated with a given bitmap block thereforeoccurs as soon as the first of the PDUs associated with this block issent, i.e. when the PDU of the block having the smallest sequence numberis sent.

According to an advantageous characteristic of the invention, for agiven bitmap block, this method comprises a first step of deactivatingsaid timer after a predetermined maximum duration, and said data packetsof said block are then considered by said transmitter in saidunacknowledged state.

As part of the H/2 ARQ protocol, this predetermined maximum durationcorresponds to the maximum round trip time RTTmax. Thus, when the timerindicates that a time greater than or equal to RTTmax has elapsed sincethe transmission of the first PDU associated with the block, and when nocorresponding feedback message has been received for this block, thetransmitter then considers that a transmission error may have occurred,and that the corresponding PDUs are in principle unacknowledged. Thetimer is deactivated automatically when RTTmax times out.

According to a second advantageous characteristic of the invention, fora given bitmap block, this method comprises a second step ofdeactivating said timer when said transmitter receives a cumulatedacknowledgement at least of said data packets of said block, indicatingthat said data packets of said block are in said acknowledged state.

Therefore, if for instance the receiver sends a feedback messageindicating that all PDUs with sequence numbers comprised between 0 and10 have been received correctly, upon receipt of this cumulated feedbackmessage by the transmitter, the timer associated with bitmap block 0,corresponding to PDUs 0 to 7, is then deactivated.

According to a third advantageous characteristic of the invention, for agiven bitmap block, this method comprises a third step of deactivatingsaid timer, when said transmitter receives a feedback message comprisingat least said bitmap block.

Preferably, upon receipt by the transmitter of said feedback message,this method implements a step of analysing said feedback message, inorder to determine said acknowledged or unacknowledged state of each ofsaid data packets of said block.

As part of the H/2 ARQ protocol, if such a feedback message comprisese.g. a single bitmap block, the transmitter then starts to read thevalues 0 and 1 of the 8 consecutive bits of this block. A 0 value bitindicates that the PDU, the sequence number of which is equal to theposition of this bit, is in unacknowledged state.

As part of an ARQ protocol, during this step of analysing a bitmapblock, the transmitter only considers PDUs whereof the sequence numberis comprised in the current transmission window, i.e. between BoW andBoW+K_(s), according to the terms previously used in this document.

Advantageously, at the end of said step of deactivating said timer, atleast one data packet of said block being in said unacknowledged state,a step of positioning at least some of said unacknowledged data packetsof said block in a retransmission queue is implemented.

This retransmission queue can be a physical queue, e.g. in the form of abuffer, wherein PDUs waiting for retransmission are stored. Positioninga PDU into the queue can also consist in associating therewith aretransmission flag, which is up when the PDU is to be retransmitted,and down otherwise. More generally, positioning a PDU in theretransmission queue can consist in indicating that it is in a specificstate prior to retransmission via any suitable technique.

As described before, the PDUs associated with a 0 value bit in thebitmap block received, but the sequence number of which is greater thanBoW+K_(s), also called EoW (End of Window) are not taken into accountduring the step of analysing the feedback message, and therefore are notpositioned in the retransmission queue.

According to an advantageous alternative of the invention, at the end ofsaid analysing step, this method implements a step of checking thepresence, in said retransmission queue, of at least one acknowledgeddata packet of said block, and, when the presence in said queue of atleast one acknowledged data packet of said block has been confirmed, itimplements a step of deleting said acknowledged data packet(s) of saidblock from said retransmission queue.

Thereby, superfluous retransmission of positively acknowledged PDUs isavoided. This technique is particularly interesting when, e.g. a timerhas timed out after a RTTmax duration, some PDUs of the correspondingblock have been prepared for retransmission, and a feedback message,positively acknowledging some of the PDUs ready for retransmission, isthen received by the transmitter, before the latter has been able toperform retransmission of the PDUs placed in the queue. The transmittercan then decide to remove from the queue the PDUs that have beenpositively acknowledged by the receiver.

According to an advantageous technique of the invention, this methodimplements at least one step of retransmitting said data packet(s) ofsaid block positioned in said retransmission queue, and a second step ofactivating said timer of said block when the first of said data packetsof said block positioned in said queue is retransmitted.

Thus, the PDUs of the queue that have not been acknowledged by thereceiver are retransmitted and the timer is triggered again when the PDUwith the smallest sequence number of the associated block isretransmitted.

Preferably, this transmission method implements an ARQ (Automatic RepeatRequest) type protocol.

This ARQ protocol can be for instance of the Selective Repeat, or GoBack N type. In particular, the invention is applied as part of the ARQSRPB (Selective Repeat with Partial Bitmap) protocol of the HiperLAN/2standard.

According to a preferred embodiment of the invention, this transmissionmethod furthermore comprises at least one time stamping step ofassociating a time stamp with at least some data packets in saidunacknowledged state.

This time stamp can be expressed in frames, or any other time measuringunit, and in particular in milliseconds. As part of the H/2 ARQ protocolwhere frames have a fixed duration of 2 ms, expressing the value of atime stamp in milliseconds allows for better precision, in comparisonwith expressing the measurement in frames.

Preferably, said time stamp is activated when said transmitter sendssaid associated data packet.

Consequently, the time stamp allows the time that has elapsed since aPDU has been transmitted to be evaluated at any time.

According to another advantageous technique of the invention, saidpositioning step comprises a preliminary sub-step of selecting datapackets to be positioned in said queue, depending on at least onepredetermined selection criterion.

Preferably, said selection criterion takes into account at least onepiece of the information belonging to the group composed of:

-   -   the value of said time, stamp associated with a unacknowledged        data packet of said block;    -   the ARQ class of said receiver.

Indeed, the value of a time stamp and the ARQ class of the receiver areindicators, respectively, of the time that has elapsed since thecorresponding PDU has been transmitted, and the time required by thereceiver for processing the PDU and transmitting a correspondingfeedback message. Taking into account either of these two criteria, orboth criteria at the same time, the transmitter can make a subtledecision as to whether it is necessary or not to position the PDU underconsideration in a retransmission queue.

According to a special embodiment of the invention, said selectionsub-step allows to select said unacknowledged data packet(s) of saidblock, associated with a time stamp having a greater value than saidpredetermined maximum duration.

Indeed, if a time stamp indicates that the PDU under consideration hasbeen transmitted since a time greater than RTTmax, a missingcorresponding feedback message can be considered by the transmitter astantamount to a likely transmission error.

Advantageously, said positioning step further comprises for each of saidselected data packets a sub-step of deactivating said associated timestamp.

As soon as a PDU is placed in the retransmission queue, its time stampis thus deactivated.

According to a first preferred embodiment of the invention, when allunacknowledged data packets of said block have been selected in saidselection sub-step, said time stamp takes the following value V(T)during said second activation step:V(T)=t(activation)+d _(max),

where t(activation) is the current time value during said secondactivation step, and where d_(max) is said predetermined maximumduration, and the time stamp associated with each data packet of theblock positioned in said queue is activated and takes the current timevalue during said retransmission of said data packet.

The d_(max) duration, also designated as RTTmax, can be expressed inframes, or e.g. in milliseconds. In the former case, and for frameslasting e.g. 2 ms, the equation above is then written as:V(T)=t(activation)+d_(max)*2, with V(T) and t(activation) beingexpressed in milliseconds.

According to a second preferred embodiment of the invention, at the endof said first step of deactivating said timer, if at least oneunacknowledged data packet of said block, associated with a time stamphaving a value of less than said predetermined maximum duration, has notbeen selected during said selection sub-step, this transmission methodimplements a third step of activating said timer of said block, so thatsaid timer takes the following value V(T):V(T)=V(run)+(Time stamp[i]−Time stamp[j]),

where V(run) is the value of said timer during said step of said timerrunning in said deactivated state, Time stamp[j] is the greater of saidtime stamps associated with said unacknowledged data packets of saidblock selected during said selection sub-step, and Time stamp[i] is thegreater of the values of said time stamps associated with saidunacknowledged data packets of said block that have not been selectedduring said selection sub-step.

Thus, when a timer has timed out, if at least one PDU of the block,which has been transmitted but not yet acknowledged, is not involved inretransmission, because its time stamp value is too low, the timer isimmediately reactivated according to the equation above. This equationcan also be written as V(T)=V(run)+(Time stamp[i]−Time stamp[j])*2 whenthe time stamp value is expressed in frames, and these frames have aduration of 2 ms. V(T) and V(run) are then expressed in milliseconds.

In case several PDUs have the same time stamp value Time stamp[i] orTime stamp[j], it can be envisaged to choose any of these values fromthe equation above.

Advantageously, at the end of said step of analysing said feedbackmessage, the said method implements, for each of said acknowledged datapackets of said block, a step of deactivating said associated timestamp.

According to a third preferred embodiment of the invention, at the endof said third step of deactivating said timer, if at least oneunacknowledged data packet of said block has not been selected duringsaid selection sub-step according to a decision criterion related to theARQ class of said receiver, this transmission method implements a fourthstep of activating said timer of said block, so that said timer takesthe following value V(T):V(T)=V(run)+(d _(max)−(t−Time stamp[i])),

where V(run) is the value of said timer during said step of said timerrunning in said deactivated state, d_(max) is said predetermined maximumduration, t is the current time value, and Time stamp[i] is the greaterof the values of said time stamps associated with said unacknowledgeddata packets of said block that have not been selected during saidselection substep.

As described before, the above equation can also be written as:V(T)=V(run)+(d _(max)*2−(t−Time stamp[i]))when d_(max) is expressed in frames, one frame lasting 2 ms, and t andTime stamp[i] are expressed in milliseconds. The equation can also bewritten as V(T)=V(run)+(d_(max)−(t−Time stamp[i]))*2 if d_(max) and Timestamp[i] are expressed in frames lasting 2 ms, and if t designates thecurrent frame number.

If several PDUs have the same time stamp value, any of these values canbe chosen from the equation above.

The invention also relates to a transmitter, a receiver, and a datatransmission system implementing the data transmission method describedpreviously.

Other features and advantages of the invention will be more apparentfrom reading the following description of a preferred embodiment,provided by way of example only and not to be restrictive, and theappended drawings, where:

It will be noted that FIGS. 2 to 4 can illustrate the special case of anARQ transmitter located in access point AP, and a receiver located in amobile terminal MT. If a communication between two terminals in directmode is considered, wherein both terminals are then transmitting duringthe same phase, FIGS. 2 to 4 can also illustrate the special case wherethe first terminal transmitting in the frame is the ARQ transmitter andwhere the second terminal transmitting in the frame is the ARQ receiverfor the communication under consideration.

The general principle of the invention is based on associating a timerwith at least some bitmap blocks transmitted by the receiver to thetransmitter.

In the course of this document, we will set out to describe anembodiment of the invention as part of the ARQ SRPB (Selective Repeatwith Partial Bitmap) protocol of the HiperLAN/2 standard. It is recalledthat, of course, the invention is also applicable to other types of datatransmission protocols, based on error detection at the time oftransmission and on retransmission of lost or damaged data.

Referring to FIG. 1, the various implementation steps according to thebasic inventive mechanism will be described briefly as part of the PDUexchanges between an ARQ transmitter and receiver. These steps will bedescribed more in detail with reference to FIGS. 2 to 5.

During a step referenced as 10, according to the method of thisinvention, at least one timer is associated with some or all of theacknowledgement blocks, also called bitmap blocks, that an ARQ receiveris likely to transmit to an ARQ transmitter, within a feedback message.According to the ARQ protocol of the HiperLAN/2 standard, such a bitmapblock is associated with 8 consecutive PDUs, and activates the selectiveacknowledgement of each of these PDUs.

The timer is activated during a step referenced as 11, during thetransmission of the first of the consecutive PDUs associated with theblock under consideration. It is then deactivated during a later stepreferenced as 12, after a predetermined maximum duration has expired orupon receipt of an acknowledgement of at least some of the PDUs of theblock under consideration.

When the timer is deactivated, the ARQ transmitter implements a step 13of selecting the possible unacknowledged PDU(s) to be retransmitted tothe ARQ receiver, then positions 14 the selected PDUs in theretransmission queue.

When the first PDU of the block, wherewith the timer is associated,positioned at the end of the queue, is retransmitted 15 thecorresponding timer is reactivated 11.

Now, referring to FIG. 2, we are going to present an embodiment ofhandling the timers associated with the bitmap blocks sent by thereceiver, as part of the PDU exchanges between a transmitter 1 and areceiver 2.

The PDU exchanges are organized in frames, designated f₀ to f₇ in FIG.2. According to the ARQ protocol of the HiperLAN/2 standard, theseframes last 2 ms.

It is considered that the transmitter and the receiver of FIG. 2 are ofARQ class 0, i.e.:

-   -   after having received in frame f_(i) a message indicating the        state of acknowledgement of several PDUs, the ARQ transmitter is        able to retransmit in the same frame f_(i) (or in the        consecutive frame according to whether its transmission phase is        before or after that of the receiver) the unacknowledged PDU(s),        provided it has the required resources;    -   after having received one or more PDUs in frame f_(i), the ARQ        receiver is able to transmit to the transmitter, in the same        frame f_(i), (or in the consecutive frame according to whether        its transmission phase is before or after that of the        transmitter) one (or several) feedback message for the PDU(s)        received if it has the required resources.

Furthermore, it is considered that the maximum duration of an operatingcycle, hereafter called RTTmax (Round Trip Time), is equal to 3 frames.

First of all, we are going to examine the bitmap block associated withthe PDUs of sequence numbers 0 to 7, which will hereafter be designatedas BMB₀ (bitmap block). At the time to, which corresponds to thebeginning of frame f₀, the value of BMB₀ is 00000000, indicating thatthe PDUs with sequence numbers 0 to 7 are all in unacknowledged state.According to the invention, a timer T₀ is associated with BMB₀.

In frame f₀, transmitter 1 sends the PDUs with sequence number 0 to 4 toreceiver 2. Timer T₀ is activated at time t₀+Δ₀, when the PDU withsequence number 0 is transmitted, designated as PDU(0). It will bedeactivated at the latest after a RTTmax duration equal to 3 frames,i.e. 6 ms, as part of the HiperLAN/2 standard, i.e. that T₀ will bedeactivated at the latest at time t=t₀+6+Δ₀.

As indicated in FIG. 2, PDU(0) and PDU(4) have been received correctlyby receiver 2. On the other hand, an incident (symbolized by a cross onthe PDU transmission arrow) has occurred during transmission of PDU(1),PDU(2), and PDU(3).

In frame f₁, which starts at time t₁, transmitter 1 sends PDU(5), whichis not received correctly, PDU(6), PDU(7), and PDU(8). When PDU(8) istransmitted, at time t₁+Δ₁, transmitter 1 activates timer T₁ associatedwith BMB₁ corresponding to PDUs with sequence numbers 8 to 15. T₁ willbe deactivated at the latest at time t₁+6+Δ₁, after a duration equal toRTTmax.

When PDU(8) has been received, receiver 2 sends a feedback message totransmitter 1 containing BMB₀ with a value equal to 10001011. Uponreceipt of BMB₀, transmitter 1 deactivates T₀, analyses the feedbackmessage, and determines that PDU(1), PDU(2), PDU(3), and PDU(5) have notbeen acknowledged, and must therefore be retransmitted.

Frame f₂ starts at time t₂. Being of ARQ class 0, transmitter 1retransmits PDU(1) and PDU(2) to the receiver 2, in frame f₂. During theretransmission of PDU(1), at time t₂+Δ₂, timer T₀ associated with BMB₀is reactivated, for a maximum duration equal to t₂+6+Δ₂.

In the same frame f₂, transmitter 1 receives a feedback message fromreceiver 2 containing BMB₀, of value 11101011. It then deactivates timerT₀, analyses the feedback message, and determines that PDU(3) and PDU(5)are still in unacknowledged state and must therefore be retransmitted toreceiver 2.

In frame f₃, transmitter 1 is assigned the resources required fortransmitting PDU(3), PDU(5), PDU(9), and PDU(10). Again, when PDU(3) istransmitted at time t₃+Δ₃, transmitter 1 activates T₀, for a maximumduration equal to t₃+6+Δ₃.

In frame f₄, transmitter 1 has the resources required for transmittingPDU(11) and PDU(12), which receiver 2 receives improperly, asillustrated in FIG. 2. In the same frame f₄, receiver 2 sends a feedbackmessage comprising BMB₀ and BMB₁. However, an incident occurs in thecourse of the transmission of this feedback message, which is notreceived by transmitter 1.

In frame f₅, transmitter 1 thus proceeds with transmitting PDU(13),PDU(14), and PDU(15). At time t′₅, timer T₁ expires after RTTmax, andtherefore goes into deactivated state. Transmitter 1 then deducestherefrom that none of the PDUs associated with BMB₁ is in acknowledgedstate, and that all the PDUs associated with BMB₁ are therefore to beretransmitted. As there is still one resource available, and being ofARQ class 0, transmitter 1 thus starts to retransmit PDU(8) in the sameframe f₅ at time t₅+Δ₅, and then reactivates T₁, for a maximum durationof t₅+Δ₅+6.

In frame f₆, transmitter 1 retransmits PDU(9). Again, timer T₀ goes intodeactivated state, after RTTmax, specifying to transmitter 1 theunacknowledged state of PDU(3) and PDU(5). The retransmission queuemaintained by transmitter 1 is then updated, in order to comprise thePDUs with the following sequence numbers: {3, 5, 10, 11, 12, 13, 14,15}. Sorting the PDUs of the queue by ascending order of sequencenumbers activates transmitter 1 to determine that it must retransmit, inframe f₆, PDU(3), PDU(5), then PDU(10). Timer T₀ is again reactivatedduring transmission of PDU(3). After the PDUs with sequence number 3, 5,and 10 have been retransmitted, the retransmission queue is updated andcomprises the PDUs with the following sequence numbers: {11, 12, 13, 14,15}.

After having correctly received PDU(10), receiver 2 sends a feedbackmessage to transmitter 1 comprising BMB₀=11111111 and BMB₁=11100110.Upon receipt of this message, T₁ and T₀ are deactivated.

According to a particularly advantageous embodiment of the invention,transmitter 1 analyses the feedback message received, determines thatPDU(13) and PDU(14) have been acknowledged by receiver 2, and deletesthem from the retransmission queue, so that is now contains the PDUswith sequence numbers {11, 12, 15}.

In frame f₇, transmitter 1 thus retransmits PDU(11), PDU(12), andPDU(15). In frame f₈, receiver 2 transmits a feedback message comprisingBMB₁=11111111, which, when received by transmitter 1, leads todeactivation of timer T₁.

All PDUs with sequence numbers 0 to 15 have then been acknowledged, andthe retransmission queue maintained by transmitter 1 is now empty.

Referring to FIG. 3, we are now going to present a second embodiment ofthe invention, wherein, in addition to a timer being associated witheach of the bitmap blocks, a time stamp is associated with eachunacknowledged PDU.

Again, an ARQ class 0 transmitter and receiver are under consideration,but now, a RTTmax duration of 2 frames is considered, i.e. 4 ms forHiperLAN/2 where frames last 2 ms.

Again, we will examine frames numbered f₀ to f₇. A timer T₀ isassociated with bitmap block BMB₀, associated with PDUs numbered 0 to 7.Also, a time stamp H_(i) is associated with the PDU having sequencenumber i, the value of which is expressed in frames, and which isactivated during transmission of PDU(i).

Thus, in FIG. 3, transmitter 1 sends the PDUs numbered 0 to 4 in framef₀. At PDU(0) transmission time t₀+Δ₀, T₀ is activated, which will bedeactivated at the latest after a duration equal to RTTmax, i.e. at timet₀+Δ₀+4. At the end of frame f₀, time stamps H₀ to H₄ are thereforeactivated and have a value of 0, and time stamps H₅ to H₇ aredeactivated.

In frame f₁, transmitter 1 transmits PDUs numbered 5 to 7. Time stampsH₅ to H₇ therefore take the value of 1. Furthermore, receiver 2 sends afeedback message comprising BMB₀=11010100 to transmitter 1, whichanalyses this message, and, receiver 2 being of ARQ class 0, deducestherefrom that the PDU5 numbered 2, 4, 6, and 7 have not beenacknowledged and must therefore be retransmitted. Upon receipt of thisfeedback message, all the time stamps H_(i) of PDUs 0 to 7 aredeactivated, as well as timer T₀.

In frame f₂, transmitter 1 retransmits PDU(2) at t₂+Δ₂ and thenreactivates T₀ for a maximum duration equal to RTTmax, then retransmitsPDU(4). Then, H₂ and H₄ are obtained, activated and equal to 2; theother time stamps H_(i) of the PDUs of BMB₀ are deactivated.

In frame f₃, transmitter 1 retransmits PDU(6) and PDU(7), and receiver 2sends a feedback message containing BMB₀, which is not correctlyreceived by transmitter 1. H₆ and H₇ are then activated at value 3. Att′₄=t₂+Δ₂+4, timer T₀ is deactivated. Transmitter 1 must then determine,during a step referenced as 20, which are the PDUs that must bepositioned in a queue for subsequent retransmission.

Transmitter 1 then analyses the value, expressed in frames, of the timestamps associated with the various unacknowledged PDUs of BMB₀, i.e.PDU(2), PDU(4), PDU(6), and PDU(7). f(t) designates the number of theframe to which belongs time t. For PDUs 2, 4, 6, and 7, the following isobtained:f(t′ ₄)−H ₂=4−2=2≧RTTmaxf(t′ ₄)−H ₄=4−2=2≧RTTmaxf(t′ ₄)−H ₆=4−3=1<RTTmaxf(t′ ₄)−H ₇=4−3=1<RTTmax

It is deduced therefrom that PDUs 6 and 7 must not be retransmitted, asthey have been sent too recently to be sure that receiver 2 hasprocessed them: indeed, only one frame has passed between theirtransmission and deactivation of T₀. Transmitter 1 then places PDU(2)and PDU(4) in the retransmission queue, and timer T₀ is reactivatedimmediately at:T ₀ =V(run)+(H _(i) −H _(j))

where V(run) is the value of T₀ during deactivation thereof, H_(i) isthe time stamp value of the oldest unacknowledged PDU of BMB₀ not to beretransmitted, and H_(i) is the value of the oldest unacknowledged PDUof BMB₀ to be retransmitted.I.e., T ₀ =t′ ₄+(H ₆ −H ₂)*2 in msI.e., T ₀ =t′ ₄+2 in ms.

Transmitter 1 then retransmits PDU(2) and PDU(4) in frame f₄.Consequently, the retransmission queue is empty, and H₂=H₄=4 and H₆=H₇=3is obtained. T₀ is deactivated in frame f₅ at time t′₅. Transmitter 1then reiterates the calculation performed above, in order to determine,during the step referenced as 21, which are the unacknowledged PDUs ofBMB₀ to be positioned in the retransmission queue:f(t′ ₅)−H ₂=5−4=1<RTTmaxf(t′ ₅)−H ₄=5−4=1<RTTmaxf(t′ ₅)−H ₆=5−3=2≧RTTmaxf(t′ ₅)−H ₇=5−3=2≧RTTmax

It is deduced therefrom that PDUs 2 and 4 must not be retransmitted, asthe time that has elapsed between their latest transmission anddeactivation of T₀ is less than RTTmax, and it is therefore possiblethat these PDUs have not yet been processed by receiver 2: therefore, itseems to be normal for these two PDUs that the transmitter has notreceived a corresponding feedback message.

PDU(6) and PDU(7) are placed in the retransmission queue, and T₀ isimmediately reactivated and takes the value defined by the equationabove:T ₀ =V(run)+(H _(i) −H _(j))

I.e., T₀=t′₅+(H₂−H₆)*2 in ms (as PDU(2) is the oldest unacknowledged PDUof BMB₀ not to be retransmitted, and PDU(6) is the oldest unacknowledgedPDU of BMB₀ to be retransmitted)I.e., T ₀ =t′ ₅+2 in ms.

In frame f₅, transmitter 1 retransmits PDU(6). The retransmission queuethen only contains PDU(7), and H₂=H₄=4, H₆=5, and H₇=3 is obtained.Transmitter 1 then receives a feedback message comprising BMB₀=11011110from receiver 2. All time stamps associated with PDUs 0 to 7 are thendeactivated, and PDU(7) and PDU(2) are positioned in the retransmissionqueue.

In frame f₆, PDU(7) is retransmitted at time t₆+Δ₆, and T₀ isreactivated and takes the value T₀=t₆+Δ₆+4. H₇ is also reactivated andtakes the value 6, and PDU(7) is deleted from the retransmission queue.

In frame f₇, transmitter 1 transmits PDU(2), H₂ is then activated andtakes the value 7, and the retransmission queue is then empty. Receiver2 sends a feedback message containing BMB₀=11111111 acknowledging all ofPDUs 0 to 7, but that a transmission incident is preventing correctreception by transmitter 1.

At time t′₈, in frame f₈, T₀ is deactivated. Transmitter 1 must thendetermine, during the step referenced as 22, which are theunacknowledged PDUs of BMB₀ that must be positioned in theretransmission queue. For this purpose, it analyses the value of thetime stamps associated with PDU(2) and PDU(7), in order to determine thetime that has elapsed between the latest transmission of these PDUs anddeactivation of T₀:f(t′ ₈)−H ₂=8−7=1<RTTmaxf(t′ ₈)−H ₇=8−6=2≧RTTmax

Only PDU(7) is placed in the retransmission queue, as it has been sent asufficiently long time ago for receiver 2 to have processed andacknowledged it. A missing feedback message for PDU(7) thereforeindicates a possible transmission error.

Timer T₀ is immediately reactivated and takes the value T₀=t′₈+(H₂−H₇)*2in ms, i.e. T₀=t′₈+2.

In frame f₈, transmitter 1 receives a feedback message comprising bitmapblock BMB₀=11111111, indicating that receiver 2 has correctly receivedall PDUs with sequence numbers 0 to 7. All time stamps H₀ to H₇ are thendeactivated, as is timer T₀.

The mechanisms implemented by the ARQ transmitter and receiver in FIG. 4are similar to those illustrated in FIG. 3, and therefore, they are notdescribed in further detail in this document. FIG. 4 shows an ARQ class0 transmitter and receiver, for which the RTTmax duration is fixed at 10frames, i.e. 20 ms as part of the HiperLAN/2 ARQ protocol.

It will be noted that at the end of the step referenced as 31, it isdetermined that PDU(0) must be positioned in the retransmission queuefor subsequent retransmission. However, in the same frame f₁₁, andbefore it has been possible to retransmit PDU(0), transmitter 1 receivesa feedback message from receiver 2 comprising bitmap blockBMB₀=11111111, indicating that receiver 2 has correctly received PDU(0).Transmitter 1 therefore detects that it is not necessary to retransmitPDU(0) and implements a step 30 of deleting PDU(0) from theretransmission queue.

Referring to FIG. 5, we are now going to describe a sampleimplementation of the invention as part of data packet (PDU) exchangesbetween an ARQ class 0 transmitter and an ARQ class 1 receiver. d_(RX)=1(expressed in frames) designates the processing time of ARQ class 1receiver. Suppose that RTTmax=3 frames, i.e. 6 ms, and frames f₀ to f₇are considered, during which PDU(0) to PDU(7) are transmitted. Timer T₀is associated with bitmap block BMB₀, and a time stamp H_(i) isassociated with each PDU(i).

In frame f₀, starting at time t₀, transmitter 1 transmits PDU(0) toPDU(4). When PDU(0) is transmitted, timer T₀ associated with block BMB₀is activated and takes the value T₀=t₀+6+Δ₀. Time stamps H₀ to H₄ areactivated and take the value 0, thus indicating that PDUs 0 to 4, withwhom they are associated, have been transmitted in frame f₀.

In frame f₁, transmitter 1 then transmits PDUs numbered 5 to 7, and timestamps H₅ to H₇ are then activated and take the value 1. At time t′₁, inframe f₁, transmitter 1 receives a feedback message from receiver 2comprising bitmap block BMB₀=10101000. When this message is received,timer T₀ is deactivated.

Transmitter 1 then implements an analysis of this feedback message, inorder to determine, during a step referenced as 40, the unacknowledgedPDUs of block BMB₀ that are be positioned in the retransmission queue.

This step 40 consists in evaluating the time, expressed in frames, thathas elapsed between transmission of a PDU and deactivation of timer T₀.For PDU(0) to PDU(4), f(t′₁)−H_(i)=1≧d_(RX) is obtained. Consequently,it is deduced therefrom that the feedback message received transportsthe actual state of acknowledgement of PDUs 0 to 4: PDUs 1 and 3 aretherefore in unacknowledged state.

On the other hand, for PDU(5) to PDU(7), f(t′₁)−H_(i)=1−1=0<d_(RX) isobtained. Consequently, it is deduced therefrom that PDUs 5 to 7 cannotbe involved by the feedback message received at time t′₁. Indeed, giventhe class of receiver 2, they have been sent too late for the latter tohave had the time to receive them, process them and send a correspondingfeedback message to transmitter 1 before time t′₁.

At the end of step 40, transmitter 1 therefore determines that onlyPDU(1) and PDU(3) must be positioned in the retransmission queue. TimerT₀ is then reactivated immediately and takes the following value:T ₀ =V(run)+(RTTmax−(f(t′ ₁)−H _(i))),where V(run) is the value of timer T₀ when it is deactivated, f(t′₁) isthe current time value expressed in frames, and H_(i) is the value ofthe time stamp associated with the oldest unacknowledged PDU of BMB₀ notto be retransmitted. Thus:T ₀ =t′ ₁+(RTTmax−(f(t′ ₁)−H ₅))*2T ₀ =t′ ₁+(3−(1−1))*2T ₀ =t′ ₁+6 in ms

is obtained.

The time stamps of PDU(1) and PDU(3) are then deactivated, as are thoseof PDU(0), PDU(2), and PDU(4), which have actually been acknowledged.

During frame f₂, transmitter 1 retransmits PDU(I), which is not receivedcorrectly by receiver 2, and time stamp H₁ is then activated and takesthe value 2. The retransmission queue now only contains PDU(3). In framef₃, transmitter 1 sends PDU(3), the corresponding timer H3 is activatedand takes the value 3, and the retransmission queue is now empty.

In frame f₄, receiver 2 sends a feedback message comprisingBMB₀=10111101, but due to a transmission incident, transmitter 1 doesnot receive it. At time t′₄ in frame f₄, timer T₀ therefore times outafter RTTmax. Transmitter 1 then implements a step 41 of determining,depending on the H_(i) time stamp values of the unacknowledged PDUs, andthe ARQ classes of transmitter 1 and receiver 2, the PDU(s) to bepositioned in the retransmission queue.

For PDU(1) and PDU(3):f(t′ ₄)−H ₁=4−2=2<RTTmax, andf(t′ ₄)−H ₃=4−3=1<RTTmax

are obtained, respectively.

It is deduced therefrom that PDUs 1 and 3 have been transmitted toorecently to be sure that receiver 2 has had time enough to receive them,process them, and send a corresponding feedback message. Consequently,PDU(1) and PDU(3) must not be retransmitted.

On the other hand, for PDUs 5 to 7:f(t′ ₄)−H ₅=4−1=3≧RTTmax, andf(t′ ₄)−H ₆=4−1=3≧RTTmax, andf(t′ ₄)−H ₇=4−1=3≧RTTmax

are obtained.

The time that has elapsed between transmission of each of PDUs 5 to 7 inframe 1, and timer T₀ timeout is sufficient for the receiver to havesent a feedback message relating to these PDUs. If this acknowledgementis missing, transmitter 1 makes the decision of positioning PDU(5),PDU(6), and PDU(7) in the retransmission queue.

The corresponding timer T₀ is reactivated immediately and takes thevalue:T ₀ =V(run)+(H _(i) −H _(j))

where V(run) is the value of T₀ when it is deactivated, H_(i) is thetime stamp value of the oldest unacknowledged PDU of BMB₀ not to beretransmitted, and H_(j) is the value of the oldest unacknowledged PDUof BMB₀ to be retransmitted.I.e., T ₀ =t′ ₄+(H ₁ −H ₅)*2 in msI.e., T ₀ =t′ ₄+2 in ms.

Time stamps H₅, H₆, and H₇ are deactivated.

Indeed, PDU(1) is the oldest unacknowledged PDU of BMB₀ not to beretransmitted, and PDU(5) is the oldest unacknowledged PDU of BMB₀ to beretransmitted.

Suppose e.g. that no transmission resource is assigned to transmitter 1in frame f₅. At time t′₅, timer T₀ is deactivated after RTTmax withoutany acknowledgement having been received for the PDUs of BMB₀.

Transmitter 1 carries out another step 42 of determining theunacknowledged PDUs to be retransmitted, implementing calculationssimilar to those exposed above:f(t′ ₅)−H ₁=5−2=3≧RTTmax, andf(t′ ₅)−H ₃=5−3=2<RTTmax.

Only PDU(1) can then be positioned in the retransmission queue, as thetime that has elapsed between transmission of PDU(3) and T₀ timeout istoo little to be sure that receiver 2 has already been able to processPDU(3).

Therefore, transmitter 1 places PDU(1) in the retransmission queue,which thus contains the sequence numbers of the following PDUs:{5,6,7}∪{1}.

Timer T₀ is immediately reactivated and takes the value:T ₀ =V(run)+(H _(i) −H _(j)) as above.I.e. T ₀ =t′ ₅+(H ₃ −H ₁)*2 in msI.e. T ₀ =t′ ₅+2 in ms.

Time stamp H₁ is deactivated, and H₃ is thus the only time stamp stillactive among all the PDUs associated with BMB₀.

In frame f₆, transmitter 1 has sufficient resources to transmit all thePDUs of the queue. Time stamps H₁ and H₅ to H₇ are then activated andtake the value 6, and the retransmission queue is then empty. Moreover,at time t′₆, transmitter 1 receives a feedback message comprising BMB₀10111101, and then deactivates T₀.

Upon receipt of BMB₀, transmitter 1 implements a step 43 of determiningthe unacknowledged PDU(s) of BMB₀ to be positioned in the retransmissionqueue. For this purpose, it evaluates the time that has elapsed betweentransmission of each of the unacknowledged PDUs (in particular PDU(1)and PDU(6)) and deactivation of T₀:f(t′ ₆)−H ₁=6−6=0<d _(RX), andf(t′ ₆)−H ₆=6−6=0<d _(RX).

Given the ARQ class of receiver 2, PDU(I) and PDU(6) are in principlenot involved by the feedback message received at t′₆. It is notnecessary to position them in the retransmission queue. Timer T₀ isimmediately reactivated and takes the value:T ₀ =V(run)+RTTmax−(f(t′ ₆)−H _(i))),where V(run) is the value of timer T₀ when it is deactivated, f(t′₆) isthe current time value expressed in frames, and, H_(i) is the time stampvalue associated with the oldest unacknowledged PDU of BMB₀ not to beretransmitted. Thus:T ₀ =t′ ₆+(RTTmax−(f(t′ ₆)−H ₁))*2T ₀ =t′ ₆+(3−(6−6))*2T ₀ =t′ ₆+6 in ms

is obtained.

The time stamps of positively acknowledged PDUs 5 and 6 are deactivated.

In frame f₇, transmitter 1 receives another feedback message comprisingBMB₀ 11111111, which allows deactivation of T₀ and indicates that allPDUs associated with BMB₀ have been correctly acknowledged. Allcorresponding time stamps are deactivated.

1. A method for transmitting data between a transmitter and a receiver,comprising: transmitting packets of data by said transmitter; receivingat the transmitter a feedback message from said receiver, the feedbackmessage including a bitmap block including a predetermined plural numberof fields associated with corresponding said packets of data, each fieldof said fields representing a consecutive identifier corresponding toeach packet of the transmitted packets and indicative of a state ofacknowledgement of each packet of said packets; associating a timer witha periodic reception of the bitmap block at the transmitter;deactivating said timer after a maximum duration, and then consideringsaid packets associated with said bitmap block to be in anunacknowledged state by said transmitter; and after deactivating saidtimer, and when at least one packet associated with said bitmap block isin said unacknowledged state, positioning at least some unacknowledgedpackets associated with said bitmap block in a retransmission queue. 2.The method according to claim 1, further comprising activating saidtimer when said transmitter sends to said receiver a first of saidpackets having consecutive identifiers associated with said bitmapblock, and switching said timer to an activated state.
 3. The methodaccording to claim 1, wherein said receiving includes receiving saidfeedback message including said bitmap block with every field indicatingthe state of acknowledgement as acknowledged.
 4. The method according toclaim 1, further comprising deactivating said timer when saidtransmitter receives a cumulated acknowledgement of said packetsassociated with said bitmap block, indicating that said packetsassociated with said bitmap block are in said acknowledged state.
 5. Themethod according to claim 1, further comprising deactivating said timer,when said transmitter receives a feedback message including said bitmapblock.
 6. The method according to claim 5, further comprising: upon thetransmitter receiving said feedback messages analyzing said feedbackmessage to determine said acknowledged or unacknowledged state of eachof said packets associated with said bitmap block.
 7. The methodaccording to claim 6, further comprising: after analyzing said feedbackmessage, for each of said acknowledged packets associated with saidbitmap block, deactivating a time stamp associated with at least somepackets in said unacknowledged state.
 8. The method according to claim 1further comprising: analyzing said feedback message to determine saidacknowledged or unacknowledged state and checking for a presence, insaid retransmission queue, of at least one acknowledged packetassociated with said bitmap block, and when the presence in said queueof at least one acknowledged packet of said block has been confirmed,deleting said at least one of said acknowledged packets associated withsaid bitmap block from said retransmission queue.
 9. The methodaccording to claim 1, further comprising: retransmitting said packet(s)of said block positioned in said retransmission queue, and activatingsaid timer associated with said block when a first of said packetsassociated with said bitmap block positioned in said queue isretransmitted.
 10. The method according to claim 1, further comprising:communicating with an ARQ (Automatic Repeat Request) protocol.
 11. Themethod according to claim 1, further comprising: associating a timestamp with at least some packets in said unacknowledged state.
 12. Themethod according to claim 11, further comprising: activating said timestamp when said transmitter sends said associated packet.
 13. The methodaccording to claim 1, wherein said positioning includes sub-selectingpackets to be positioned in said queue, depending on a selectioncriterion.
 14. The method according to claim 13, wherein said selectioncriterion takes into account at least one of a value of a time stampassociated with an unacknowledged packet associated with said block andan ARQ class of said receiver.
 15. The method according to claim 13,wherein said sub-selecting includes selecting an unacknowledged packetassociated with said block and associated with a time stamp having avalue greater than or equal to said maximum duration.
 16. The methodaccording to claim 11, wherein said positioning includes for each ofsaid selected packets, deactivating said associated time stamp.
 17. Themethod according to claim 9, wherein when all unacknowledged packetsassociated with said bitmap block have been selected in saidsub-selecting, said timer takes a value V(T) wherein,V(T)=t(activation)+d _(max), where t (activation) is a current timevalue, and where d_(max) is said maximum duration, wherein the timerassociated with each packet of the bitmap block positioned in said queueis activated and takes the current time value during said retransmissionof said packet.
 18. The method according to claim 15, furthercomprising: after deactivating said timer, if at least oneunacknowledged packet of said block, associated with said time stamphaving a value of less than said predetermined maximum duration, has notbeen selected during said sub-selecting, activating said timer of saidbitmap block, so that said timer takes a value V(T):V(T)=V(run)+(Time stamp(i)−Time stamp(j)), where V(run) is the value ofsaid timer during said timer running in said deactivated state, Timestamp(j) is the greater value of said time stamps associated with saidunacknowledged packets associated with said bitmap block selected duringsaid sub-selecting, and Time stamp(j) is the greater value of said timestamps associated with said unacknowledged packets associated with saidbitmap block not selected during said sub-selecting.
 19. The methodaccording to claim 14, further comprising: after deactivating saidtimer, if at least one unacknowledged packet of said bitmap block hasnot been selected during said sub-selecting depending on a decisioncriterion related to the ARQ class of said receiver, activating saidtimer of said block so that said timer takes a value V(T):V(T)=V(run)+(d _(max)−(t−Time stamp(i))), where V(run) is a value ofsaid timer during said timer running in said deactivated state, d_(max)is said maximum duration, t is a current time value, and Time stamp (i)is the greater value of said time stamps associated with saidunacknowledged packets associated with said bitmap block not selectedduring said sub-selecting.